Platelet activating factor (PAF) is a phospholipid released from human and other animal cells and is an acetylglyceryl ether of phosphorylcholine as represented by the following formula: ##STR2## where n is 15 or 17.
PAF is physiologically active and causes contraction of the airway smooth muscle, increased vascular permeability, platelet aggregation, hypotension, and the like. It is now recognized as a powerful mediator of inflammation and may play a physiological or pathobiological role in a variety of clinical conditions, such as asthma and pulmonary dysfunction, rhinitis, acute inflammation, transplanted organ rejection, shock, thrombosis, anaphylaxis, gastrointestinal ulceration, allergic skin diseases, retinal and corneal diseases, chemically induced liver cirrhosis, and ovimplantation in pregnancy. Accordingly, compounds possessing PAF antagonistic effects should be of value in the treatment of any of the above conditions.